Ten plots of 0.1-0.05 ha were laid out from 140 m to 560 m above sea level at intervals of 25-70 m. The gradient analysis revealed that distributions of many plant species terminated or started at ca. 400 m. Community similarity, calculated in Percentage Similarity (PS) and Community Coefficient (CC), changed abruptly below and above the 400 m contour, suggesting a change of vegetation structure at this elevation. The spacial turnover rate of species along the altitudinal gradient was calculated in two ways. The average turnover rate, by plotting the log similarity values on the Y-axis against altitudinal difference between plots on the X-axis, was low in tree and shrub species and high in herbaceous species. The zone turnover rate, calculated for an altitude as the average rate among the three neighbouring plots, was high at the 370-440 m belt. This coinsided with the abrupt interchanging pattern in species distributions. Species density per 100 m^2 increased from low to high altitudes, while other indices of speices diversity, S_(100), b, α and H', decreased along the same gradient in all population categories studied.